Spinning-mill preparing machine with a control apparatus

ABSTRACT

A method is suggested for operating a spinning-mill preparing machine ( 1 ) with a control apparatus ( 20 ), especially a draw frame, card or combing machine, in which a running fiber structure (FV) is conducted through a measuring area ( 26, 26′,33 ) of a measuring apparatus ( 25, 25′, 32 ) and a measuring signal (S(t); S a (t), S e (t)) is generated that represents the length-specific mass (M) of the fiber structure (FV) located in the measuring area ( 26, 26′,33 ), in which a corrected measuring signal (SK(t); SK a (t), SK e (t)) is generated in that a correction value (K 0 , K 1 , K 2 ; K a , K e ) is added to the measuring signal (S(t); S a (t), S e (t)), and in which the determination of the correction value (K 0 , K 1 , K 2 ; K a , K e ) takes place by the following steps controlled by the control apparatus ( 20 ) of the spinning-mill preparing machine ( 1 ): 
         The fiber structure (FV) is removed from the measuring area ( 26, 26′,33 ) by pneumatic and/or mechanical means ( 27, 13,14; 28 ), Then, an empty measuring is performed, and    The correction value (K 0 , K 1 , K 2 ; K a , K e ) is calculated in that the empty measuring value obtained in this manner (SL 0 , SL 1 , SL 2 ) is subtracted from a theoretical value (SL Soll ) of the measuring signal (S(t); S a (t), S e (t)) which value is predefined for an empty measuring.

The present invention relates to a method for operating a spinning-millpreparing machine with a control apparatus, especially a draw frame,card or combing machine, in which a running fiber structure is conductedthrough a measuring area of a measuring apparatus and a measuring signalis generated that represents the length-specific mass of the sliverlocated in the measuring area. The present invention also concerns aspinning-mill preparing machine, especially a draw frame, card orcombing machine, with a control apparatus and at least one measuringapparatus for generating a measuring signal that represents thelength-specific mass of a fiber structure conducted through themeasuring area of the measuring apparatus.

In a short-staple spinning mill at first a rather long fiber structureis produced from raw fibers that have a length of a few centimeters inseveral process steps. The raw fibers can consist of cotton, variousartificial fibers or of a mixture of the same.

In a process for the manufacture of yarn that is customary at thepresent a closed fiber structure is manufactured by a card from fed rawfibers. In the card an areal fiber structure, a so-called fiber fleece,is produced at first that is then combined to a strand-shaped fiberstructure, generally called a sliver. This sliver is evened out furtherby following draw frames and optionally by combing machines. The sliverproduced in this manner is finally fed to a spinning machine forproducing a twisted yarn.

The quality of the spun yarn depends in particular on the uniformity ofthe fed sliver. Therefore, spinning-mill preparing machines are providedwith apparatuses for evening out and monitoring the uniformity of thefiber structure. Such apparatuses for evening out or monitoring thequality are connected to sensors that detect the length-specific mass ofthe sliver. The length-specific mass of a fiber fleece or of a sliver isindicated in the dimension of mass per unit of length and is at the sametime a measure for the thickness of the fiber structure at a certainlocation.

It has been known for some time that the mass and the thickness of arunning fiber structure can be detected by mechanical scanning systems.Furthermore, contactless sensors have been suggested that operate, e.g.,according to a capacitive measuring process, an irradiation process, areflection process or according to a resonance process.

Independently of the measuring principle, sensors for detecting thesliver mass and/or sliver thickness have a characteristic curve thatdescribes the connection between the mass of the fed sliver or fiberfleece and between a generated output signal. It is known in order tomonitor the observance of a defined theoretical characteristic curve ofa mechanical scanning system that a plurality of measuring gauges ofdifferent but known thicknesses can be fed to the particular scanningsystem. Such gauges are also designated as check gauges. The thicknessof the different check gauges is distributed over the measuring area ofthe sensor. In as far as differences are determined between the actualoutput signal and the particular theoretical output signal of the sensorthe sensor is manually readjusted.

However, such a compensating method can not be used in the case ofsensors operating in a contactless manner. It is also hardly possible tocompensate a contactless sensor by feeding fiber structures with adefined mass since the latter can not be manufactured with the requiredaccuracy. Furthermore, drafts conditioned by the manipulation and due tothe loose inner cohesion of a fiber structure can not be avoided, sothat the fed fiber structure would change its length-specific massduring a compensation procedure. It is therefore necessary as a rule inorder to compensate a contactless sensor to check a fiber structuremeasured by the sensor subsequently in the lab and then adapt the sensormanually, for which several iteration steps are normally necessary.

Such manual methods for compensating a sensor for detecting the fiberstructure thickness in a spinning-mill preparing machine require a lotof time and are therefore only performed in practice upon the occurrenceof serious quality deviations in the manufactured fiber structure.

Deviations of measurement of a sensor that are located in the intervalbetween two such steps for sensor compensation can not be detected inthis manner and consequently also not be corrected. In particular,short-term fluctuations in the environmental conditions such as, e.g.,variations in temperature or changes in the air humidity result inmeasuring errors that result on the one hand in a deterioration of theaction of the evening-out apparatuses and on the other hand inunsatisfactory quality data. However, even other error sources areproblematic such as, e.g., mechanical wear or contamination of thesensor.

The present invention has the goal of eliminating the described problemsin conjunction with the detection of the sliver mass or thickness in arunning fiber structure in a spinning-mill preparing machine.

This goal is achieved with a method for operating a spinning-millpreparing machine as well as with a spinning-mill preparing machine withthe features of the independent claims.

In a method in accordance with the invention a correction of themeasuring signal of the measuring apparatus takes place in that acorrection value is added to the measuring signal and that thedetermination of the correction value takes place by following stepscontrolled by the control apparatus of the spinning machine. At first,the fiber structure is removed from the measuring area by pneumaticand/or mechanical means. In other words, the measuring area and thefiber structure are separated from one another spatially in such amanner that the fiber structure to be actually measured no longerinfluences the measuring signal. Then, an empty measuring is carried outand the correction value calculated in that the empty measured value ofthe measuring signal obtained by the empty measuring is subtracted froma predefined theoretical value of the measuring signal. In the method ofthe invention the complicated feeding of fiber structure specimens witha defined mass can be completely eliminated. The method can also becarried out in a few seconds.

The measuring area of a measuring apparatus is that spatial area inwhich the mass of the fiber structure is detected by the particularmeasuring method. The concept “measuring area” is therefore to beabstractly understood. It is of no significance whether the measuringarea is defined physically or conceptually.

Once a correction value has been determined, it is used for correctingthe measuring signal until a new correction value is determined. As aconsequence of the low amount of time involved, the determination of newcorrection values can take place in relatively short time intervals. Thecorrection value can assume positive or negative values and the propersign of the addition to the measuring signal is to be observed. Thesuggested method can be used in continuous or discrete measuringmethods. It is also of no consequence whether the measuring signal ispresent in digital or in analog form. The predefined theoretical valueof the measuring signal in an empty measuring can be taken from thetheoretical characteristic curve of the measuring apparatus ordetermined in a phase prior to operation.

The fiber structure can be removed from the measuring device in anespecially simple manner for performing an empty measuring if ameasuring device is used whose measuring area transverse to thelongitudinal direction of the running fiber structure is open at leaston one side. The fiber structure can then be removed from the measuringarea by moving the fiber structure relative to the measuring area or themeasuring area relative to the fiber structure transversely to thedirection of movement of the fiber structure.

In this instance it is advantageous if the measuring area is moved andthe fiber structure left in its original position. This can avoid anerroneous drafting of the sensitive fiber structure. The measuring areacan be moved here in a straight line and/or in a curved line.

However, it is also conceivable to remove the fiber structure from themeasuring area with a movable fiber structure guidance means, e.g., witha roller, hook, eyelet or a grasper.

It is also possible to remove the fiber structure from the measuringarea by separating it upstream from the measuring area and by drawingthe downstream section of the fiber structure out of the measuring area.

The determination of a new correction value preferably takes place whena deviation of quality is determined in the produced fiber structure byan automatic quality detection system associated with the spinning-millpreparing machine. The determination of a new correction value can takeplace for a sensor that supplies measuring signals directly to thequality detection system as well as for any other sensor.

The determination of a new correction value is advantageously initiatedregularly after the passage of a certain time span. This takes placewithout an operational intervention automatically by the controlapparatus. Likewise, the determination of a new correction value can beinitiated regularly after a certain length of the fiber structurerunning through. In both instances a regular correction of the measuringsignal of the measuring apparatus is ensured.

The fiber structure is frequently deposited in a spinning can at thedischarge of a spinning-mill preparing machine. Filled cans must beregularly replaced by empty cans. It is appropriate in this instance tocontrol the empty measuring for determining the correction value by thecontrol apparatus in such a manner that it takes place regularly duringa can replacement. The determination of the correction value can takeplace at each can replacement or, e.g., at each second or third canreplacement.

Furthermore, it is possible that the determination of a correction valueis automatically initiated alternatively or additionally immediatelyafter the turning on the spinning-mill preparing machine by the controlapparatus. In this instance the determination of a new correction valuetakes place independently of whether a can replacement is necessary ornot. Changes in the environmental conditions such as, e.g., thetemperature, that occurred during the service life of the spinning-millpreparing machine are therefore directly taken into consideration. Theregular new determination can nevertheless continue to be carried outduring a can replacement.

It is advantageously provided that the determination of a new correctionvalue is initiated, even outside of any regular new determination of thecorrection value provided, by the control apparatus when the correctedmeasuring signal reaches a set threshold value. In this instance inparticular an upper and a lower threshold value can be defined. In thisinstance a reaching or even a dropping below the upper boundary value aswell as a reaching or a dropping below the lower boundary value resultin a new determination of the correction value. If the old and the newcorrection values do not differ substantially from one another, thisindicates an actual change of the mass of the fiber structure.Otherwise, a change in the measuring behavior of the measuring apparatusis obviously present.

The presetting of threshold values that can be defined absolutely orrelatively can be checked automatically to see whether unusually high orunusually low values of the corrected measuring signal are based on anactual increase or decrease of the mass of the fiber structure or, e.g.,on a change (drift) of the measuring behavior of the measuringapparatus. In the former instance a warning notice can then be emittedso that the operator is made aware of the unusual deviation of the massof the fiber structure. If necessary, an interruption of the manufacturecan also take place in order to prevent unnecessary waste. In the latterinstance the drift of the measuring apparatus is automatically correctedby the new correction value.

It can also be provided that a new determination of the correction valueis initiated by the control apparatus when the corrected measuringsignal rises or falls by more than a set amount within a certain timespan. The plausibility of such unusual measured values can also beautomatically checked in this instance. If necessary, the alreadymentioned measures can be initiated.

It can be additionally or alternatively provided that the determinationof the correction value is initiated by an operator action. Thus, thedetermination of a correction value is also possible outside of theprovided cycles if, e.g., there is justified doubt about the correctfunctioning of the measuring apparatus. The determination of thecorrection value itself then takes place without additional input of theoperator by the control apparatus of the spinning-mill preparingmachine.

It is especially advantageous if the fiber structure is threaded intothe measuring area after the empty measuring by pneumatic and/ormechanical means controlled by the control apparatus and is supplied toa pulling-off means controlled by the control apparatus and arrangeddownstream from the measuring area. The pulling-off means can be, e.g.,a pair of pulling-off rollers. In this instance the manual threading inof the fiber structure is eliminated after an empty measuring.

It is especially advantageous if the manufacture of the spinning-millpreparing machine is automatically started after the threading in andsupplying to the pulling-off means. In this manner interruptions ofmanufacture can be reduced to a minimum.

It is furthermore advantageous if the measuring area is cleaned afterthe removal of the fiber structure and before the empty measuring. Thiscan prevent influences of contamination on the measuring signal.Contaminations frequently consist of accumulations of particles offibers or of dirt. The cleaning of the measuring area is advantageouslycontrolled by the control apparatus of the spinning-mill preparingmachine.

The measuring area can be cleaned by a fluid, e.g., by compressed orsuction air and/or by mechanical cleaning means.

A warning notice is preferably emitted and/or the spinning-millpreparing machine brought to a standstill if the determined correctionvalue exceeds a predefined threshold value. This is appropriate sinceespecially large deviations between the theoretical value and the actualvalue in an empty measuring indicate an especially strong contaminationand/or a defective functioning of the spinning-mill preparing machine. Awarning notice puts the user in the position of reacting appropriately.A stopping of the spinning-mill preparing machine prevents unnecessarywaste.

In principle, the measuring signal can be generated using any knownphysical method. However, a mechanical scanning method, a capacitivemeasuring method, an irradiation method, a reflection method and/or aresonance method is/are preferably used for generating the measuringsignal. The performing of a resonance method using microwaves isespecially preferred since in this manner the mass and/or thickness ofthe fiber structure can be measured independently of the materialmoisture.

In an advantageous embodiment the running fiber structure is conductedthrough a measuring area of a measuring apparatus arranged at the inletof the spinning-mill preparing machine and through a measuring area ofanother measuring apparatus arranged at the outlet of the spinning-millpreparing machine and the measuring signal of the measuring apparatus atthe inlet is corrected by a correction value and the measuring signal ofthe measuring apparatus at the outlet is corrected by another correctionvalue. As a result thereof, very accurate measured values can be madeavailable for the regulation (open-loop and/or closed-loop control) ofthe spinning-mill preparing machine or for the quality monitoring.

It is appropriate that the measuring apparatus arranged at the inlet iscompensated if unusual measuring results occur in the measuringapparatus at the outlet. This is especially valid if the correctedmeasuring signal of the measuring apparatus arranged at the outletreaches or exceeds a predefined upper threshold value or predefinedlower threshold value, or if the corrected measuring signal of themeasuring apparatus arranged at the outlet rises or falls by more than afixed amount within a certain time span, or if the further correctionvalue reaches or exceeds a fixed maximum correction value or a minimumcorrection value.

It is especially advantageous if the determination of a new furthercorrection value for correcting the measuring signal of the measuringapparatus at the outlet is initiated automatically by the controlapparatus if the corrected measuring signal of the measuring apparatusarranged at the outlet reaches or exceeds a predefined upper thresholdvalue or a predefined lower threshold value, or if the correctedmeasuring signal of the measuring apparatus arranged at the outlet risesor falls by more than a fixed amount within a certain time span, or ifthe previous further correction value reaches or exceeds a fixed maximumcorrection value or a minimum correction value.

If the newly determined further correction value deviates from theprevious further correction value by less than a predetermined amount,this indicates a defective functioning of the regulation in front of themeasuring apparatus at the outlet. In this instance the determination ofa new correction value for correcting the measuring signal of themeasuring apparatus at the inlet is automatically initiated by controlapparatus 20. To the extent that the defective functioning of theregulation was based on a defective correction value of the measuringapparatus at the inlet, it is now corrected. Otherwise, e.g., an alarmcan be released.

A spinning-mill preparing machine in accordance with the inventioncomprises a correction member for the addition of a correction value tothe measuring signal. In this instance the control apparatus of thespinning-mill preparing machine is designed to control a method fordetermining the correction value using at least one empty measuring.This can eliminate a manual compensation of the measuring apparatus ofthe spinning-mill preparing machine.

Means for removing the fiber structure from the measuring area areadvantageously present that can be controlled by the control apparatus.This can eliminate even the manual removal of the fiber structure.

If the measuring area is open at least on one side transversely to thelongitudinal direction of the fiber structure the means for removing thefiber structure can advantageously be designed in such a manner that arelative movement is possible between the fiber structure and themeasuring area transversely to the direction of movement of the fiberstructure. This can avoid a separating of the fiber structure.

However, if the measuring area is closed on all sides so that itsurrounds the fiber structure on all sides the means for removing thefiber structure can be designed in such a manner that the fiberstructure can be separated upstream from the measuring area, for whichpull-off means, e.g., calender rollers are provided for drawing thedownstream section of the fiber structure out of the measuring area. Forexample, means comprising cutting or tearing tools can be provided forseparating the fiber structure. Alternatively, a thin area can beproduced in the fiber structure by an appropriate controlling of theroller pairs of a draw frame located in front, which thin area wouldresult in a separation of the fiber structure. It is immaterial in thisinstance whether the roller pairs are driven via a regulatingtransmission by a common motor or by individual drives. It is possiblein both instances to separate the fiber structure by differences inspeed between the roller pairs. Likewise, the separation can take placein that the draw frame located in front is entirely stopped whilemaintaining the clamping of the fiber structure but the pull-off meanscontinues to be driven.

It is especially advantageous if the control apparatus is designed forautomatically initiating the determination of the correction value. Thisinitiation regularly takes place in an advantageous manner after theexpiration of a certain time span or after a certain amount or length ofthe fiber structure running through.

The control apparatus can also be designed to initiate the determinationof a correction value after the spinning-mill preparing machine has beenturned on.

If a depositing can is arranged downstream from the measuring apparatusthe control apparatus can be designed to initiate the determination ofthe new correction value during a can replacement.

The spinning-mill preparing machine is advantageously designed toautomatically initiate the determination of the correction value whenthe corrected measuring value reaches a fixed a threshold value.

The spinning-mill preparing machine can also be designed in such amanner that it automatically initiates the determination of thecorrection value if the corrected measuring signal rises or falls bymore than a set amount within a certain time span.

If the control apparatus is connected to an operating element it isadvantageous if the control apparatus is designed to initiate thedetermination of the corrected value after an operator action. Anoperator-initiated new determination of the correction value can also beperformed, e.g., during the filling of a can that is, when no canreplacement is taking place.

Furthermore, it is preferred that pneumatic and/or mechanical means forthreading in the fiber structure and controlled by the control apparatusis present in the measuring area, which control apparatus is designed toautomatically initiate the threading in after an empty measuring. Thethreading in brings about a feed of the fiber structure to a pull-offmeans controlled by the control apparatus and arranged downstreamrelative to the measuring area. It can be, e.g., a pair of calenderrollers.

The control apparatus is advantageously designed to independently startthe production after the threading in and the feeding of the fiberstructure to the pull-off means.

It can additionally be provided that means controllable by the controlapparatus is provided for cleaning the measuring area with mechanicalcleaning agent or a fluid supplied under pressure, preferably bycompressed or suction air. The control apparatus is designed in thisinstance to automatically initiate a cleaning procedure.

Furthermore, the control apparatus can be designed to control theemitting of a warning notice, e.g., by an output device connected to thecontrol apparatus and/or to initiate a cutoff of the spinning-millpreparing machine if the correction value exceeds a predefined value.

The measuring apparatus is advantageously designed to carry out amechanical scanning process, a capacitive measuring process, anirradiation process, a reflection process and/or a resonance process.

Other advantages of the invention are described in the followingexemplary embodiments.

FIG. 1 shows a sketch of a draw frame in accordance with the state ofthe art.

FIG. 2 shows a sketched partial view of a draw frame in accordance withthe invention.

FIG. 3 shows a detailed view of an alternative embodiment.

FIG. 4 shows a presentation of an uncorrected measuring signal and of acorrected measuring signal over the course of time.

FIG. 1 shows draft frame 1 as an example for a spinning-mill preparingmachine in accordance with the state of the art. However, the inventionalso relates to other spinning-mill preparing machines, in particularcards or combing machines to the extent that they comprise a controlapparatus 20 and at least one measuring apparatus 25, 25′, 32 forgenerating a measuring signal S(t) representing the length-specific massof a fiber structure conducted through a measuring area 26, 26′, 33 ofthe measuring apparatus.

Six individual slivers FB are fed adjacent to each other toschematically shown draw frame 1. Slivers FB are shown from abovewhereas draw frame 1 is shown as such in a lateral view. Funnel 12 isarranged at the input to draw frame 1 and compresses slivers FB to asingle fiber structure FV. After having run through a first measuringapparatus that generates a measuring signal S_(e)(t) representing thelength-specific mass of fiber structure FV that was conducted throughit, the now compressed fiber structure FV is conducted into draw frame 4forming the core piece of the draw frame.

Draw frame 4 comprises entrance roller pair 5 a, 5 b, middle roller pair6 a, 6 b and exit or also delivery roller pair 7 a, 7 b that rotate witha circumferential speed that is increased in this sequence. As a resultof these different circumferential speeds of the roller pairs, fiberstructure FV, that is spread out like a fleece in the draw frame, isdrafted according to the ratio of the circumferential speeds.

Entrance roller pair 5 a, 5 b and middle roller pair 6 a, 6 b form theso-called pre-drafting field, and middle roller pair 6 a, 6 b anddelivery roller pair 7 a, 7 b the so-called main drafting field. Inunregulated draw frames both the pre-draft and the main draft areconstant during the drafting procedure. On the other hand, in regulateddraw frames a compensatory regulation of fluctuations in the mass of thefiber composite takes place by changing the draft height. In thisinstance the main draft is usually changeable since the main draft is asa rule greater that the pre-draft, so that a more accurate compensatoryregulation of variations in thickness of the fiber structure can takeplace.

Pressure rod 8 additionally arranged in the main draft field deflectsfiber structure FV and thus ensures a better guidance of the fibers. Thedrafted fiber structure FV is then deflected with the aid of upperdeflection roller 9 and fed to sliver forming apparatus 10. Sliverforming apparatus 10 is designed as funnel 10 and serves to compress thefiber fleece to a unified sliver. Measuring apparatus 25 is arranged atthe output of funnel 10 and comprises measuring area 26 in which themass of fiber structure FV that was conducted through it is detected.This mass and/or thickness is converted into a measuring signal 5 a(t)by sensor electronics (not shown).

Measured fiber structure FV is pulled off by calander roller pair 13, 14and fed to depositing can 24. Depositing can 24 comprises rotary plate17 rotating about its vertical axis of plane and with sliver conduit 16for depositing fiber structure FV into can 18. Can 18 itself is moved bymeans (not shown) in the case of a square can translatorily and in thecase of a round can rotationally relative to stationary rotary plate 17.As a result thereof, the entire inner area of can 18 can be filled withdeposited fiber structure FV. Once a can 18 has been completely filledit can be replaced with an empty can manually by an operator or by canreplacement device 19 (shown only schematically).

Draw frame 1 comprises control apparatus 20 that controls in particularthe speed of the roller pairs of draw frame 4. To this end it acts onthe drives (not shown) of the roller pairs. Likewise, control apparatus20 acts on roller pair 2, 3 at the entrance of the draw frame, on thecalender roller pair 13, 14 at the exit of the draw frame and on thespeed of rotary plate 17 of depositing can 24. Furthermore, controlapparatus 20 can be designed to control can replacement apparatus 19. Asis customary, control apparatus 20 is connected to operating apparatus22, e.g., a keyboard, and to output unit 23, e.g., a viewing screen.

In addition, draw frame 1 comprises quality monitoring system 21designed to monitor the quality of the fiber structure produced.

The first measuring apparatus 32 comprises measuring area 33 and twoscanning disks 2, 3 of which scanning disk 2 is designed to bestationary and scanning disk 3 is pressed with pressure against scanningdisk 2 and can be deflected vertically to its axis of rotation. Thedeflections of scanning disk 3 are a measure for the mass of fiberstructure FV. The deflection is produced e.g., with an inductive sensor(not shown) that generates measuring signal S_(e)(t). Measuring signalS_(e)(t) is then taken from control apparatus 20 for changing thepre-draft and/or the main draft of draw frame 4. This can stabilizefluctuations of the mass of the fiber structure. Such a method is alsodesignated as open-loop control of the draw frame.

Measuring apparatus 25 at the outlet of draw frame 4 comprises measuringarea 26 through which fiber structure FV is conducted and measured in acontactless manner. The using of a contactless sensor is especiallyadvantageous here since the speed of the running fiber structure at theoutlet of the draw frame is by nature clearly greater than at itsentrance side. Measuring signal S_(a)(t), that is generated by measuringapparatus 25 by sensor electronics (not shown) is evaluated by qualitydetection system 21. In particular, the average thickness of the sliverand the non-uniform areas remaining in the fiber structure are detected.If the quality of the exiting fiber structure does not meet therequirements, e.g., a signal can be transferred from quality detectionapparatus 21 to control 20 and the machine can be stopped. Also, areport to the operator can be made, e.g., via output unit 23.

Measuring signal S_(a)(t) of measuring apparatus 25 at the outlet ofdraw frame 4 is frequently also directly transmitted to controlapparatus 20. Thus, e.g., the spinning-mill preparing machine can be cutoff autonomously by control apparatus 20 on account of deficientquality. It is also conceivable that measuring signal S_(a)(t) can beused to control the draft of draw frame 4. The closed-loop controlrealized in this manner is particularly suitable for stabilizinglong-term deviations in the direction of the theoretical value.

On the whole, an optimal stabilization of fluctuations of the runningfiber structure is only possible if the measuring signals S(t) ofmeasuring apparatuses 32, 25 used for this are sufficiently accurate.Also, an expressive determination of quality is only possible with acorrespondingly accurate measuring signal S_(a)(t) of measuringapparatus 25.

Measuring apparatuses of spinning-mill preparing machines are thereforecompensated or adjusted in complicated manual methods. To this end checkgauges with known thicknesses are manually presented in mechanicallyscanning measuring apparatuses and the measuring signals S(t) comparedwith the theoretical value in accordance with the theoreticalcharacteristic curve of the particular measuring apparatus. Thiscustomarily takes place with a plurality of check gauges with differentthicknesses that cover the entire measuring area of the particularmeasuring apparatus. After such measuring series have been manuallyperformed the particular measuring apparatus is then compensated orreadjusted. In contactless measuring systems measuring results of themeasuring apparatus are subsequently checked in the laboratory. In thecase of deviations the sensor characteristic is changed in iterativesteps until an appropriate coincidence of the measured results of thesensor and of the results measured in the laboratory occurs.

Such compensating methods can only be carried out at relatively largetime intervals on account of the relatively high cost. However,influencing magnitudes on measuring signal S(t) that rapidly change intime can therefore not be detected and falsifications occurring as aresult thereof cannot be corrected. Falsifications of measuring signalS(t) produced by a change of temperature of the measuring apparatus canbe cited here. Also, falsifications of the measured results can takeplace due to contamination adhering in the measuring apparatus.Falsifications of the measured results due to temperature influences orcontamination emerge in a more or less pronounced manner in all knownmeasuring methods.

FIG. 2 shows part of a draft frame 1 in which measuring signal S_(a)(t)of measuring apparatus 25 arranged at the exit as well as measuringsignal S_(e)(t) of measuring apparatus 32 arranged at the entrance arecorrected in a manner in accordance with the invention. However, theinvention could just as well be realized exclusively at the entrance orexclusively at the exit of the draw frame.

The invention will first be explained in detail using the example ofmeasuring apparatus 25 arranged at the exit. Measuring apparatus 25detects the mass of fiber structure FV running through in the manneralready described and generates a measuring signal S_(a)(t) from it.This measuring signal S_(a)(t) is fed to correction member 31 _(a).Correction member 31 _(a) is formed for the addition of a correctionvalue K_(a) to measuring signal S_(a)(t). Corrected measuring signalSK_(a)(t) generated in this manner can be used in the manner alreadydescribed for carrying out a closed-loop control by control apparatus 20as well as for detecting the quality of the fiber structure by qualitydetection apparatus 21. Correction value K_(a) is determined by a methodthat is completely controlled by control apparatus 20.

In the example shown, correction value K_(a) is calculated by controlapparatus 20 and mediated to correction member 31 _(a). Alternatively,correction member 31 _(a) could be designed to independently calculatecorrection value K_(a). It is also possible to integrate correctionmember 31 _(a) into control apparatus 20. Correction value K_(a) isdetermined by an empty measuring and used for correcting measuringsignal S_(a)(t) until a new value K_(a) is determined. The determinationof a new correction value K_(a) takes place upon the occurrence of apredetermined condition by control 20. Such a condition can be anoperator action on input unit 22, the expiration of a certain time or acertain length of fiber structure FV conducted through measuringapparatus 25. The determination of a new correction value K_(a)advantageously takes place during a necessary can replacement.

When can 18 located under rotary plate 17 is full, control apparatus 20initiates the replacement of spinning can 18 by can replacementapparatus 19 provided for this purpose. At the same time a separation ofthe fiber structure takes place by means 27 for separating the fiberstructure and controlled by control apparatus 20. Means 27 is designedand arranged in such a manner that the separation of fiber structure FVtakes place upstream from measuring apparatus 25. Means 27 forseparating the fiber structure can comprise, e.g., cutting or tearingtools. Alternatively, a thin area could be produced in the fiberstructure by appropriately regulating the roller pairs of draw frame 4,which would result in a separation of the fiber structure. Likewise, theseparation can take place in that draw frame 4 is entirely stopped whilemaintaining the clamping of fiber structure FV but calender roller pair13, 14 continues to be driven. The only important factor is that theseparation takes place upstream from measuring area 26.

After the separation the fiber structure consists of an upstream sectionFV_(ab) and of a downstream section FV_(zu). Calender roller pair 13, 14is now controlled in such a manner by control 20 that downstream sectionFV_(ab) of the fiber structure is completely removed from measuring area26 of measuring apparatus 25. At the same time the transport of theupstream section of fiber structure FV_(zu) is interrupted by controlapparatus 20. Measuring area 26 of measuring apparatus 25, that has nowbeen emptied, can now be cleaned with the aid of means 30 for cleaningthe measuring area. Means 30 for cleaning measuring area 26 can becontrolled by control apparatus 20. The actual cleaning of measuringarea 26 takes place by blowing in compressed air, which is indicated bythe arrow in dotted lines. Means 30 could alternatively or additionallybe designed for cleaning measuring area 26 by suction air and/or bymechanical means.

An empty measurement takes place after the cleaning of measuring area 26during which empty measuring value SL₀ is compared with theoreticalvalue SL_(soll). Correction value K is determined by subtractinginstantaneous value SL₀ of measuring signal S_(a)(t) from giventheoretical value SL_(soll). If necessary, even several emptymeasurements could be carried out successively during which theparticular results for determining correction value K_(a) could beaveraged.

The threading in of the front end of the upstream section of fiberstructure FV into measuring area 26 of measuring apparatus 25 takesplace after the empty measurement. To this end control apparatus 20transmits control impulses to pneumatic threading-in means 29. At thesame time control commands to the rollers of draw frame 4 occur, so thatthe upstream section of the fiber structure is transported further. Thethreading of the fiber structure into measuring area 26 takes place bythe controlled emission of impulses of compressed air into funnel 10,which is indicated by the arrow in dotted lines. The threading-in couldalso take place by suction air or a combination of suction air andcompressed air.

The compressed air flow generated by threading-in apparatus 29 and theformation of measuring area 26 and its relative arrangement to calenderroller pair 13, 15 bring it about that the front end of fiber structureFV, which has now been threaded in, can be grasped and pulled off bycalender roller pair 13, 14. Calender roller pair 13, 14 is arranged forits part in such a manner relative to rotary plate 17 that fiberstructure FV that is now running is automatically introduced into sliverconduit 16.

The described method can be carried out within the time span that isrequired in any case for an automatic can replacement. It can thereforebe performed several times daily or even several times hourly withoutlimiting the productivity of the draw frame. Falsifications of measuringsignal S_(a)(t) of measuring apparatus 25, e.g., due to contamination,temperature influences or to environmental influences can be rapidlycorrected. It is not necessary to differentiate between the variousdisturbing influences. Although the method for operating thespinning-mill preparing machine is preferably carried out completelyautomatically, it can also be used in principle if the spinning-millpreparing machine does not have an automatic can replacement device 19available. Thus, it can be provided that the full can is removed by anoperator and replaced by an empty can. In this instance the threading inof the separated fiber structure and the resumption of production takeplace only after an operator action in order to prevent a sliver frombeing produced without an available spinning can.

Measuring signal S_(e)(t) of measuring apparatus 32 arranged at theinlet of draw frame 1 is corrected in an analogous manner. At first, itis transmitted to correction member 31 _(e) and converted there into acorrected measuring signal SK_(e)(t) by the addition of correction valueK_(e) determined by control apparatus 20. The determination ofcorrection value K_(e) takes place as described above in the example ofmeasuring apparatus 25 arranged at the outlet of draw frame 1 on thebasis of at least one empty measurement. Means for cleaning measuringarea 33 and means for removing sliver FV from measuring area 33 ofmeasuring apparatus 32 are not shown but could be provided at theentrance.

When the corrected measuring signal SK_(a)(t) of measuring apparatus 25arranged at the outlet reaches or exceeds a predefined upper thresholdvalue SW₀ or a predefined lower threshold value SW_(u), thedetermination of a new correction value K_(a) is automatically initiatedby control apparatus 20. This can also take place if measuring signalSK_(a)(t) rises or falls by a certain value within a certain time span.If the new correction value K_(a) does not differ substantially from theprevious correction value K_(a) this indicates an actual increase ordecrease of the mass of fiber structure FV. In addition, a certaindifference can be determined between the new and the previous correctionvalue K_(a) and when it is maintained, an actual increase or decrease ofthe mass of fiber structure FV is assumed. If the set difference isexceeded there is obviously a drift relative to the measuringcharacteristic of measuring apparatus 25 that is then compensated by thenew correction value K_(a).

In case of an actual change of the mass of fiber structure FV theregulating of the draw frame does not function satisfactorily. The causeof this can be a drift of the measuring characteristic of measuringapparatus 32 arranged at the entrance since its measuring signalsS_(e)(t) are used to regulate the draft of draw frame 4. Therefore, thedetermination of a new correction value K_(e) for measuring apparatus 32arranged at the entrance of draw frame 1 is initiated by controlapparatus 20. To the extent that the new and the old correction valuesK_(e) substantially coincide, there is obviously another disturbance anda warning notice can be emitted or the machine can be stopped in orderto avoid unnecessary waste. However, if the old and the new correctionvalues K_(a) sufficiently differ, the operation of the machine isrestarted. In this instance too a minimal difference can be set in orderto distinguish the cited instances. Finally, the observance of the giventhreshold values is again monitored by measuring apparatus 25 arrangedat the outlet and by control apparatus 20 and a warning notice or aproduction stop initiated if necessary.

FIG. 3 shows an alternative arrangement for removing fiber structure FVout of measuring area 26′, that is open to its left side and can bearranged, e.g., at the outlet of a draw frame 1 (FIG. 2). Measuring area26′ is supported in such a manner that it can be shifted transversely tothe running direction of fiber structure FV. Measuring area 26′ can bemoved to the right with the aid of means 28 controlled by controlapparatus 20 (FIG. 2) in order to remove fiber structure FV frommeasuring area 26 in order to carry out an empty measuring. Thisstraight-line shift is indicated by the double arrow. However, themovement of the measuring area can also take place in principle in acurved line, e.g., as a pivoting motion.

The measuring area could also be arranged to be stationary and the fiberstructure could be pivoted out laterally from the measuring area bycontrollable grippers, hooks, eyelets or the like. It is not necessaryin measuring apparatus 25′ according to FIG. 3 to separate fiberstructure FV in order to perform an empty measuring.

In the position of measuring area 26 shown an empty measuring can becarried out as described. Means 28 for carrying out the relativemovement between fiber structure FV and measuring area 26 is alsocontrolled by control apparatus 20. Means 28 for removing the fiberstructure from the measuring area is designed at the same time as ameans for threading in the fiber composite into measuring area 26 afteran empty measuring. During this time measuring area 26 is moved back tothe left into its initial position (see FIG. 2). In order to carry out amovement of measuring area 26 means 28 for removing and threading infiber structure FV into the measuring area comprises a pneumatic and/ormechanical drive.

FIG. 4 shows a typical course in time of measuring signal S(t) and ofcorrected measuring signal SK(t) when carrying out the method of theinvention. At a time t₀ the spinning-mill preparing machine is turned onby its main switch. Since no fiber structure is being transportedthrough the measuring area yet, measuring signal S(t) assumes the courseof a horizontal straight line at first. At time t₁ an empty measuring isautomatically performed. Since the value S(t₀) corresponds totheoretical value SL_(soll) of an empty measuring, a correction value K₀with value 0 is determined at first.

At time t₂ the production of the spinning-mill preparing machine isbegun. A fiber structure FV with the average and uniform sliver mass SBis conducted through measuring area 26 of measuring apparatus 25.Measuring signal S(t) has a wave form in this area due to the variationsof mass present in running fiber structure FV. In an ideal measuringapparatus 25 the measuring signal S(t) would oscillate around value SB.However, measuring signal S(t) of real sensor 25 present increasinglydeviates upward from line SB in the course of time. The cause for thiscan be grounded, e.g., in a temperature rise of the measuring apparatusconditioned by the operation or in increasing contamination of themeasuring apparatus.

At time t₃ a first can replacement KW₁ is initiated. Measuring signalS(t) falls to a value SL₁ after the fiber structure was removed frommeasuring area 26. At time t₄ a new empty measuring takes place.However, the measured value SL₁ obtained in this manner deviates up fromthe theoretical value of an empty measuring SL_(soll). Therefore, a newcorrection value K₁ equal to SL_(soll)−SL₁ is calculated. This newcorrection value K₁ is added at time t₅ with the proper sign tomeasuring signal S(t). The corrected measuring signal SK(t) thereforedeviates from time t₅ downward from measuring signal S(t) by value K₁.

At time t₆ the production is restarted. In this second production phasethe corrected measuring signal SK(t) deviates downward from measuringsignal S(t) at each point in time by correction value K₁. Due to thefurther increase of disturbing influences, measuring signal S(t) andcorrected measuring signal SK(t) increasingly deviate up from value SB,that corresponds to the average sliver weight. A second can replacementKW₂ takes place in time window t₇ to t₁₀. A new empty measuring iscarried out at time t₈, wherewith a new correction value K₂ iscalculated. This new correction value K₂ is added from time t₉ tomeasuring signal S(t). As a consequence thereof, corrected measuringsignal SK(t) is moved closer to its theoretical line during theresumption of production at time t₁₀.

A lower threshold value SW_(u) and an upper threshold value SW_(o) aredetermined for the corrected measuring signal. If one of the twothreshold values SW_(u), SW_(o) is reached or exceeded, which is notshown in FIG. 4, an empty measuring would take place in order todetermine a new correction value independently of the can replacementsKW₁, KW₂.

FIG. 4 serves to basically explain the operating method of the inventionfor a spinning-mill preparing machine. The courses shown for measuringsignal S(t) and for corrected measuring signal SK(t) are not showntrue-to-scale. Note concerning the course in time that that in a realproduction operation the ratio of the time of a can replacement and of aproduction phase is distinctly higher. In the exemplary instance shown,measuring signal S(t) migrates upward from its theoretical value.However, even those instances can be corrected with the method in whichthe measuring signal S(t) deviates downward from the value SB. Only thedetection of the value K with the proper sign as well as its additionwith a proper sign to measuring signal S(t) is essential here.

The present invention is not limited to the exemplary embodiments shownand described but rather modifications are possible at any time withinthe scope of the patent claims. For example, it can be provided thatseveral empty measurings (that are then to be averaged or weighted) arecarried out in order to determine a correction value.

1. A method for operating a spinning-mill preparing machine (1) with acontrol apparatus (20), especially a draw frame, card or combingmachine, in which a running fiber structure (FV) is conducted through ameasuring area (26, 26′,33) of a measuring apparatus (25, 25′, 32) and ameasuring signal (S(t); S_(a)(t), S_(e)(t)) is generated that representsthe length-specific mass (M) of the fiber structure (FV) located in themeasuring area (26, 26′,33), characterized in that a corrected measuringsignal (SK(t); SK_(e)(t), SK_(a)(t)) is generated in that a correctionvalue (K₀, K₁, K₂; K_(a), K_(e)) is added to the measuring signal (S(t);S_(a)(t), S_(e)(t)) and that the determination of the correction value(K₀, K₁, K₂; K_(a), K_(e)) takes place by the following steps controlledby the control apparatus (20) of the spinning-mill preparing machine(1): The fiber structure (FV) is removed from the measuring area (26,26′,33) by pneumatic and/or mechanical means (27,13,14; 28), Then, anempty measuring is performed, and The correction value (K₀, K₁, K₂;K_(a), K_(e)) is calculated in that the empty measuring value obtainedin this manner (SL₀, SL₁, SL₂) is subtracted from a theoretical value(SL_(soll)) of the measuring signal (S(t); S_(a)(t), S_(e)(t)) whichvalue is predefined for an empty measuring. 2-39. (canceled)